Tubing connections are commonly used medical treatment systems, chemical processing plants, pharmaceutical plants, laboratories, etc. A common class of connectors mate by mutually rotating parts of the connectors, by pushing them together, or both. One common type of connector is a luer connector which includes a relatively long male element which fits tightly in a channel of a female element. In 1970s luers were merely pushed together to make a connection. Later, threaded collars were added to make it harder for the luer connectors to come apart. Even though the threaded collar increases the reliability of the connection, in some applications, such as extracorporeal blood treatment systems, it is desirable to address even minute levels of risk, if possible. There is a need in the art for simple and inexpensive ways to increase the reliability of connectors for fluid-carrying vessels and particularly, this need is felt in the area of tubing systems used in medical treatment devices. In particular, it would be desirable to enhance the security of luer-type connectors without altering the familiar features of their design or usability.